Figure 1. U87 exosomes induce increased spontaneous firing that is independent of the synaptic input.

(A) Intracellular recordings in current clamp (I = 0) from a control hippocampal neuron (left, black trace) and a neuron incubated for 24 hours with U87 exosomes (right, blue trace). (B) Comparison of resting membrane potential (RMP; filled circles) and AP threshold (open circles). (C) Spontaneous AP frequency for both conditions. For B and C, n = 16 control, n = 20–22 treated neurons. **P < 0.01, ***P < 0.001, Mann-Whitney U test. (D) AP distribution from 8 randomly selected neurons in control and treated groups. (E) Neurons exhibiting low synaptic inputs: representative examples of voltage clamp recordings at –70 mV under control and treated conditions to obtain recordings of synaptic currents not contaminated by voltage-gated conductances. (F) Corresponding current clamp recordings from the cells in E, showing increased firing induced by U87 exosomes (blue). (G and H) Voltage clamp at –70 mV (G) and current clamp (H) obtained from a control and a U87-treated neuron exhibiting high synaptic inputs.